Add another example that sends values to influxdb

Author: micw

examples/rain_to_influx.md

@@ -0,0 +1,18 @@
+# Sending rain data (and other sensor data) to influxdb
+
+This script subscribes to a certain topic and sends all incoming values to influxdb database "iotdata". The values are tagged with a sensor id extracted from the topic.
+
+The script:
+
+```javascript
+var request = require('request');
+
+subscribe('sensor/+/rainDelta', function (topic,val,obj,prev,msg) {
+        var sensorId=topic.split("/")[1];
+        data='rain_amount,sensor='+sensorId+' value='+val;
+        request.post({
+                url: 'https://influxdb.example.com/write?db=iotdata',
+                body: data
+        });
+});
+```